The Phenotypic Switch of Human Prostate Epithelial Cells in Serum
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Prostatic carcinoma is the second most common form of cancer among human males after lung cancer. The difficulty encountered in attempting to culture adult human prostate epithelial cells has prevented sufficient studies from being undertaken to determine the etiology of prostatic carcinoma and other devastating diseases of the prostate gland. The supplementation of various nutrient media with concentrations of fetal bovine serum in excess of 5% has quickly become common practice due to its facilitation of cell growth, but is not without complications. This study addresses the observation that epithelial cells grown in RPMI 1640 nutrient medium supplemented with 10% serum, a mixture which is commonly used in the culture of prostate epithelial cells, undergo phenotypic changes to a dysplastic morphology. Prostate epithelial cells of normal morphology were maintained in WAJC 404 serum free medium, whereas those of dysplastic morphology were maintained in RPMI 1640 medium plus 10% serum. Dysplastic and normal epithelial cells were compared in terms of genetic expression of collagen and laminin, with results indicating similar expression of type IV collagen, greater expression in dysplastic cells of type I collagen and type III collagen, and greater expression in epithelial cells of laminin. The results of immunofluorescence staining indicate that the switch to dysplastic morphology is accompanied by changes in the production of such proteins as vimentin and keratin as well as such cytoskeletal elements as actin. Observations made of cells grown in WAJC 404 nutrient medium supplemented with various concentrations of serum indicate that levels of serum of 2.5% or higher in culture can result in the proliferation of significant populations of dysplastic cells. These results become significant when one considers the error which is potentially introduced into studies of prostate epithelial cells conducted in high serum environments.